How Do I Calculate Frequencies from FFT Array Elements?

FFT array of mid -frequency determination

Question:

Given the FFT results stored in the array (including the real and the virtual part), how to obtain the frequency corresponding to each array element?

Answer:

To determine the frequency related to the FFT frequency band, you can use the following formulas: The frequency band frequency = n * fs / n

Among them:

N is the frequency band index

FS is the sampling rate

N is FFT size
• Example:
Consider a FFT result, where the FS is set to 44.1 kHz and the n settings to 1024. The frequency of the first few frequency bands is as follows:

Frequency band 0: 0 Hz (DC)

frequency band 1: 43.1 Hz

Frequency band 2: 86.1 Hz

• frequency band 3: 129.2 Hz
• ... <...>
• Please note that the scope of the frequency band from 0 to N-1. For the real number input signal, the second half of the FFT contains redundant information, which can be ignored. In this example, the last useful frequency band is n/2-1 = 511, corresponding to 22006.9 Hz.
• Note:

Usually, the frequency higher than the frequency of Naquris (FS/2) will be attenuated by the anti -hybrid filter, which may not have practical significance.

Naquist frequency is represented by the frequency band of N/2.

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